This invention relates to electrosurgical devices and in particular to a probe for use in performing electrocautery and ophthalmic operations.
Electricity has been used to cauterize tissue in essentially two different ways. One technique comprises the use of an electrical current to heat a resistance element, the heated element then being applied to the tissue to be cauterized. The use of this technique precludes the necessity of applying an electrical current through the tissue. The other technique comprises the application of an alternating current through the tissue which causes cauterization in the vicinity of the electrode tip due to the high current density in this region.
Heretofore, the application of alternating current through the tissue was usually performed by using either a unipolar or bipolar technique. In the unipolar technique, the patient is placed on a ground plate which forms one electrode. The other electrode comprises a probe disposed in an insulated hand piece. The ground plate and the probe are electrically connected across the terminals of a high frequency voltage source. Using this technique, the tip of the probe is applied to the tissue. The current flows between the probe and the ground plate, with cauterization occurring in the vicinity of the probe tip due to the high current density in this region. This technique has several disadvantages, among which are the possibility of ground plate burn and cross-cardiac conduction difficulties due to the face that the current is flowing between the probe and the ground plate through the patient's body. In addition, this technique requires that the tissue area be relatively dry and uniform in order to obtain repeatable results without having to constantly adjust the output of the high frequency power supply.
The other technique involves the use of bipolar forceps as an electrosurgical instrument. Using this instrument, the destructive effects are passed between two points in the field, each blade of the forceps constituting one electrode. This instrument can be used in a wet field, and since current passes from one blade to the other, only that tissue grasped in the forceps will be coagulated and the spread of coagulation to adjacent tissue is prevented. Bipolar forceps have been used for electrocautery in tonsillectomies (See article entitled "Bipolar Forceps for Electrocautery Tonsillectomy", Reed, et al, Transactions of AAOO, Vol. 78, 1974) and has also been used in ophthalmic applications (See "Bipolar Coagulation In Ophthalmic Operations, McPherson, Jr., American Journal of Ophthamology, Vol. 73, No. 5, May 1972). In the bipolar application, the distance between the tips are variable in most cases, therefore there is variable coagulation with the same setting of the power supply. There are also forceps in which the distance between the tips is fixed. However, although the coagulation is more uniform when this type of forcep is used, the result is a linear or line coagulation or a smudge. Such linear coagulation or smudge is undesirable in microsurgery or scleral marking.